Telescoped ammunition comprising a sub-calibre projectile stabilized by a deployable tail fin

ABSTRACT

A telescoped type ammunition including a case inside which is housed a sub-calibre projectile equipped with a segmented discarding sabot, a propellant charge and an igniting device for the propellant charge, wherein the sub-calibre projectile incorporates a prolonged part receiving a tail fin able to move between a folded position against the prolonged part and a deployed position, the sabot retaining the tail fin in the folded position, the sabot encloses the tail fin to isolate it so as to prevent any contact between the tail fin and the propellant charge.

SCOPE OF THE INVENTION

The technical scope of the present invention is that of telescoped ammunition comprising a sub-calibre projectile.

STATE OF THE ART

This type of telescoped ammunition generally incorporates a substantially cylindrical case inside which a projectile and propellant charge assembly is positioned.

The projectile assembly is entirely encased in the case. It may be constituted by a single-piece projectile, at the full calibre of the weapon, or be formed by a sub-calibre projectile and a sabot, at the full calibre of the weapon, which surrounds and supports the sub-calibre projectile.

The present invention applies in particular to such telescoped ammunition containing a projectile assembly formed of a sub-calibre projectile and a sabot.

When ammunition comprising a sub-calibre projectile is fired, the projectile assembly constituted by the sabot and sub-calibre projectile is propelled in the barrel of the weapon. Upon exiting the barrel, the sabot detaches from the sub-calibre projectile, which continues its trajectory.

In order to travel on a predictable trajectory over a long distance, the projectile must be stabilized upon exiting the barrel.

This stabilization may be a spin stabilization resulting from the rapid spin of the projectile around its longitudinal axis, imparted to the projectile by the rifling of the barrel. Such stabilization is generally implemented for a projectile at the full calibre of the weapon. It may also be implemented for sub-calibre projectiles. In this case, the sliding band surrounding the sabot, and which is in contact with the rifled barrel of the weapon, imparts a spin to the projectile assembly.

However, when the projectile is a sub-calibre projectile, the spin that is transmitted to the sliding band may not be enough to satisfactorily stabilize the projectile.

Furthermore, ammunition projectiles increasingly enable loads to be embarked, such as explosive charges, electronic components or gyroscopes. Such loads may be sensitive to the projectile spinning too quickly, as this may alter their functioning.

Fin-Stabilization of the Sub-Calibre Projectile

It is also known to ensure the aerodynamic stabilization of the projectile on its trajectory by means of a tail fin. The tail fin ensures the stable trajectory of the projectile over very long distances, for example of over 3 km. Sub-calibre projectiles equipped with tail fins are generally driven in a spinning motion at a moderate speed that is lower than that of spin-stabilized projectiles.

Thus, telescoped ammunition is known, by patent FR-2647891 which corresponds to the preamble to Claim 1, a telescoped ammunition comprising a projectile assembly, constituted by a sabot and a sub-projectile equipped with a tail fin.

Limits to Fin-Stabilization According to Prior Art

Such fin-stabilization of a sub-calibre projectile may only apply, however, to projectiles of relatively reduced diameter with respect to the calibre of the weapon. Indeed, to efficiently ensure stabilization, the span of the tail fin, which must be less than the calibre of the weapon, must be greater than the diameter of the sub-calibre projectile body.

The need exists, however, for fin-stabilized projectiles of relatively large diameter able to embark explosive charges, electronic components, for example to track a moving target, or a gyroscope enabling the trajectory of the projectile to be known. Such loads effectively take up a lot of space and may be disrupted by a projectile spinning too quickly.

DESCRIPTION OF THE INVENTION

The aim of the present invention is therefore to propose telescoped ammunition, comprising a sub-calibre projectile, able to overcome such drawbacks.

In particular, the aim of the invention is namely to propose such ammunition in which the sub-calibre projectile has relatively large dimensions with respect to the calibre of the gun barrel.

Another aim of the invention is to propose such ammunition in which the sub-calibre projectile is stabilized efficiently without being subjected to an excessive spin rate likely to disrupt the functioning of the load it is embarking.

The invention thus relates to telescoped type ammunition comprising a case inside which is housed a sub-calibre projectile equipped with a segmented discarding sabot, a propellant charge and an igniting device for the propellant charge, wherein said sub-calibre projectile incorporates a prolonged part receiving a tail fin able to move between a folded position against said prolonged part and a deployed position, said sabot retaining said tail fin in said folded position.

According to one characteristic of the invention, said sabot encloses said tail fin to isolate it so as to prevent any contact between said tail fin and said propellant charge.

According to another characteristic of the invention, the tail fin comprises blades that are hinged with respect to the prolonged part of the sub-calibre projectile by means of hinges with their axes parallel to the longitudinal axis of the sub-calibre projectile.

According to yet another characteristic of the invention, each of said blades is able to move between:

1. a folded position in which each blade extends along an external surface of said sub-calibre projectile, and

2. a deployed position in which each of said blades extends radially around the prolonged part of the sub-calibre projectile.

Advantageously, said hinges are provided with limit stops preventing said blades from pivoting out of an angular range lying between said folded position and said deployed position. If need be, cotter pins may be employed to prevent the blades from closing up during the trajectory.

According to yet another characteristic of the invention, the tail fin, in said deployed position, has a diameter that is greater than the calibre.

Advantageously, the case is constituted by a substantially cylindrical casing one end of which is closed by a rear end cap, the other end being fitted with a guide tube, in which said projectile is engaged.

According to yet another characteristic of the invention, the sabot has, along at least part of its length, a substantially cylindrical external section at the full calibre and a substantially cylindrical external section at the full calibre over the full length of said sub-calibre projectile.

According to yet another characteristic of the invention, the prolonged part of the sub-calibre projectile incorporates plane faces aligned on the longitudinal axis of the sub-calibre projectile onto which the blades are folded back in their folded position.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics, details and advantages of the invention will become more apparent from the detailed description given below by way of illustration in relation to the drawings, in which:

FIG. 1 shows an axial section of ammunition according to one embodiment of the invention;

FIG. 2 shows the ammunition projectile assembly on FIG. 1, from which one part of the sabot has been removed so as to enable the sub-calibre projectile to be seen;

FIG. 3 shows the sub-calibre projectile from the ammunition in FIG. 1 out of the sabot;

FIG. 4 is a cross section of the projectile assembly of the ammunition shown in FIG. 1, taken at the tail fin of the sub-calibre projectile;

FIG. 5 is a cross section of the sub-calibre projectile in the ammunition shown in FIG. 1, out of the sabot, taken at the deployed tail fin.

DETAILED DESCRIPTION OF THE EMBODIMENTS OF THE INVENTION

The invention will now be described in greater detail.

FIG. 1 shows a cross section along the longitudinal axis of telescoped type ammunition 1. Such ammunition comprises a case, constituted by a cylindrical casing 2, closed by a rear end cap 3 and a guide tube 6.

The rear end cap 3 closes the rear end of the casing 2. It is preferentially made of metal and has, in its centre, an igniting device 4 of a known type, classically comprising a primer and an igniting relay (not described). The rear end cap 3 is connected to the casing by means of a seal 5, which may be made of a plastic material.

The guide tube 6 is position at the front end of the casing 3. It is preferably made of a plastic material and is reinforced by a metal11 c ring 7. This guide tube 6 is tubular shaped, defining an axial bore, and is at the full calibre of the weapon intended to fire the ammunition.

The case of the ammunition 1 comprises a propellant charge surrounding a projectile 9 constituted by a sub-calibre projectile 16 that is integrated into a segmented discarding sabot 11, whose front end is at the full calibre of the weapon and is engaged in the axial bore of the guide tube 6.

The projectile 9 is also shown, out of the case, in FIG. 2. In this Figure, however, only half the sabot 11 is shown so as to reveal the sub-calibre projectile 16.

This projectile 9 is intended to be propelled out of the ammunition case 1, after passing through the barrel of the weapon, under the effect of the pressure generated by the combustion of the propellant charge 8.

The sabot 11, which may be made of aluminium, has a globally cylindrical external shape, at the full calibre of the barrel of the weapon in which it is engaged. In a manner known in itself, the sabot 11 is constituted by several segments, in the embodiment shown there are four segments, which may be separated from one another upon exiting the barrel. In FIG. 2 only two such segments are shown. These four segments are held in contact with one another and against the projectile 16 by a sliding band 12 (not shown in FIG. 2) arranged to fit a peripheral groove in the sabot 11, close to the front end of such sabot 11.

This sliding band 12 is preferentially formed of a plastic material enabling its deformation during the passage of the sabot 11 in the axial bore of the guide tube 6 and then in the gun barrel. In a known manner, the sliding band 12 ensures gas-tightness between the projectile assembly 9 and the gun barrel. When the gun barrel is rifled, this sliding band 13 may also transmit a spin to the projectile assembly 9 imparted by the he11 coidal rifling of the barrel.

Upon exiting the barrel, the segments forming the sabot 11 tend to move away from each other under the effect of the centrifugal force or aerodynamic forces. This distancing causes the rupture of the sliding band 12 and the separation of the sabot segments 11 from the sub-calibre projectile 16, which continues its trajectory. The sliding band 12 may, in a known manner, have incipient fractures in order to facilitate this separation.

The sabot segments 11 are also held in contact with one another and against the sub-calibre projectile 16 by a retainer ring 13 (not shown in FIG. 2) fitted into a peripheral groove in the sabot 11 close to the rear of the sabot 11. In the same manner as for the sliding band 12, this retainer ring 13, preferably made of a plastic material, is intended to rupture during the separation of the sabot segments 11.

The sabot 11 has an axial bore shaped to receive and retain the sub-calibre projectile 16.

This sub-calibre projectile 16 is shown in FIG. 3, out of the sabot. It extends along a main axis which corresponds to the firing axis of the ammunition 1.

The sub-calibre projectile 16 is formed of several components assembled together. At its front end, it has an ogive nose cone 14, preferentially made of metal. In the embodiment shown, this ogive nose cone is made of aluminium and has small canards intended to help guide the sub-calibre projectile 16 towards its target.

The axial bore of the sabot 11 has, at the nose cone 14, an enlarged diameter to be able to surround these canards.

The nose cone 14 is mounted on the fore of a projectile body 15, preferably made of a metal11 c material such as tungsten. This projectile body 15 has a prolonged part 10 with an inner chamber 16 in which a load, such as an explosive charge of electronic components, for example to guide the projectile, may be positioned. The external surface of this projectile body 15 has threading, or peripheral grooves. The axial bore of the sabot 11 has, preferentially, at this projectile body 15, a shape that matches the threading or grooves so as to make the sabot 11 axially integral with the sub-calibre projectile 16.

This inner chamber 18 is closed, at the rear, by a cap 17.

The axial bore in the sabot 11 is itself closed at the rear by a cap 17 protecting the rear of the sub-calibre projectile 16. This cap 17 may be retained by the sabot segments 11. Preferentially, it is also attached to the igniting device 4 which ensures that the projectile assembly 16 is held in the correct position in the case.

During the combustion of the propellant charge, the pressure build-up in the ammunition causes this attachment to rupture enabling the closing plate to the propelled through the gun barrel along with the projectile assembly 16.

On the prolonged part 10 close to the rear end of the sub-calibre projectile 16 there is a tail fin 19 which, in the embodiment shown, is formed of four blades 19 a, 19 b, 19 c and 19 d angularly spaced around the tail of the sub-calibre projectile 16. Each blade is positioned in a folded position on a plane surface provided on the prolonged part 10. FIG. 3 shows the plane surface 21 onto which the blade 19 c may be folded back in the folded position.

It goes without saying that this tail fin 19 is deployable, the blades 19 a, 19 b, 19 c and 19 d being able to move between a folded position and a deployed position.

The tail fin 19 is thus shown in the folded position in FIGS. 1 and 2, and also in FIG. 4, which is a cross section of the projectile assembly 16 at the prolonged part 10 carrying this tail fin.

The tail fin 19 is shown, however, in its deployed position in FIG. 3 and in FIG. 5, which is a cross section of the sub-calibre projectile 16 at the prolonged part 10 carrying this tail fin.

To be able to move between these two positions, the blades 19 a, 19 b, 19 c and 19 d forming the tail fin 19 are each mounted able to pivot on the prolonged part 10 of the sub-calibre projectile 16 around a hinge, respectively 20 a, 20 b, 20 c and 20 d, whose axes are substantially parallel to the longitudinal axis of the sub-calibre projectile 16.

Preferably, as shown in FIGS. 5 and 6, the prolonged part 10 of the projectile 9, shown as a section view at the tail fin 19, has a substantially square external section. The hinges, respectively 20 a, 20 b, 20 c and 20 d of blades 19 a, 19 b, 19 c and 19 d, are placed along the edges of this square section, such that each blade 19 a, 19 b, 19 c and 19 d may, in its folded position, extend against each of the substantially plane square-section surfaces 21 of the prolonged part 10 of the sub-calibre projectile 16.

Preferably, the internal shape of the axial bore in the sabot 11 fits the shape, at the prolonged part 19, of the blades in this folded position, as shown in FIG. 4 which shows segments 11 a, 11 b, 11 c and 11 d of the sabot 11. The sabot 11, when surrounding the sub-calibre projectile 16, therefore, holds the blades 19 a, 19 b, 19 c and 19 d of the tail fin 19 in their closed position folded onto the corresponding plane face 21. This tail fin 19 is therefore very small in size, less than the calibre of the gun barrel.

Upon exiting the gun barrel, the segments 11 a, 11 b, 11 c and 11 d of the sabot 11 separate from the sub-calibre projectile 10, and the blades 19 a, 19 b, 19 c and 19 d are no longer held in their folded position. These blades 19 a, 19 b, 19 c and 19 d then pivot around their respective hinges 20 a, 20 b, 20 c and 20 d until reaching their deployed position.

Preferentially, this pivoting is performed under the effect of the centrifugal force and the aerodynamic forces, the pivoting of each blade from its folded to deployed positions being performed in a direction contrary to that of the projectile's 9 spin through the air. It is also possible, in other embodiments, to provide springs to push the blades from their folded position into their deployed position.

In their deployed position, the blades 19 a, 19 b, 19 c and 19 d preferably extend radially with respect to the longitudinal axis of the sub-calibre projectile 16. The hinges 20 a, 20 b, 20 c and 20 d are advantageously equipped with limit stops preventing the blades 19 a, 19 b, 19 c and 19 d from pivoting beyond this radial direction which corresponds to their deployed position.

In this position of the blades 19 a, 19 b, 19 c and 19 d, the tail fin 19 in its deployed position has a large span, greater than that of the calibre of the gun barrel. It is therefore able to effectively stabilize the sub-calibre projectile 16 which may then follow a trajectory over a long distance.

The sub-calibre projectile for telescoped ammunition according to the invention may therefore be effectively stabilized by the tail fin whilst having a large diameter with respect to the calibre of the gun barrel. This particularity gives it a greater carrying capacity than for sub-calibre projectiles for telescoped ammunition of prior art. By way of example, in the embodiment represented herein, the sub-calibre projectile has a diameter of approximately 20 mm, whereas the diameter of the weapon is of 40 mm.

The solution proposed by the invention thus enables more voluminous loads to be embarked in the projectile of telescoped ammunition. It also enables such loads to be subjected to a relatively slow spin rate, thereby reducing the risk of malfunction of the load linked to projectile spin.

It should also be noted that this solution proposed by the invention enables ammunition of relatively small calibre to be implemented equipped with a deployable tail fin and incorporating small sized mechanical elements. Such implementation is made possible by the fact that the sabot completely encloses the tail fin in its folded position. When the pressure builds up inside the ammunition, the tail fin is thus protected by the sabot, preventing it from being damaged.

A person skilled in the art may, with no difficulty, introduce variants to the solution presented, without departing from the scope of the present invention. The solution proposed by the invention may namely be adapted to telescoped type ammunition of different calibres.

The deployable tail fin according to the invention may also be implemented with a different number of blades by providing the necessary number of plane surfaces. Thus, it is possible to manufacture such a tail fin with two or three blades, or even five or six blades.

In this case, the external section of the sub-calibre projectile at the tail fin may be selected such that each of the blades may, in its folded position, extend against one of the substantially plane external faces. This section may, for example, by triangular if there are three blades, pentagonal if there are five blades or hexagonal if there are six blades.

Similarly, it is advantageous for the sabot to be divided into the same number of segments as the number of blades, but it is also possible to have a different sabot configuration. It is thus possible, for example, to assemble a sabot formed of three segments onto a sub-calibre projectile 16 with four blades. The three segments must in that case be machined so as to form together a sabot whose axial bore has a shape that matches the shape of the tail fin it its folded position. 

1. A telescoped type ammunition comprising a case inside which is housed a sub-calibre projectile equipped with a segmented discarding sabot, a propellant charge and an igniting device for the propellant charge, wherein the sub-calibre projectile incorporates a prolonged part receiving a tail fin able to move between a folded position against the prolonged part and a deployed position, the sabot retaining the tail in the folded position, the tail fin comprising blades extending radially with respect to the longitudinal axis of the sub-calibre projectile.
 2. The ammunition according to claim 1, wherein the sabot encloses the tail fin to isolate it so as to prevent any contact between said tail the tail fin and the propellant charge.
 3. The ammunition according to claim 1, wherein the tail fin comprises blades that are hinged with respect to the prolonged part of the sub-calibre projectile by means of hinges with their axes parallel to the longitudinal axis of the sub-calibre projectile.
 4. The ammunition according to claim 3, wherein each of the blades is able to move between: a folded position in which each blade extends along an external surface of the sub-calibre projectile, and a deployed position in which each of said the blades extends radially around the prolonged part of the sub-calibre projectile.
 5. The ammunition according to claim 4, wherein the hinges are provided with limit stops preventing the blades from pivoting out of an angular range lying between the folded position and the deployed position.
 6. The ammunition according to claim 1, wherein the tail fin, in the deployed position, has a diameter that is greater than the calibre.
 7. The ammunition according to claim 1, wherein the case is constituted by a substantially cylindrical casing one end of which is closed by a rear end cap, the other end being fitted with a guide tube, in which the projectile is engaged.
 8. The ammunition according to claim 1, wherein said the sabot has, along at least part of its length, a substantially cylindrical external section at the full calibre.
 9. The ammunition according to claim 8, wherein said the sabot has a substantially cylindrical external section at the full calibre over the full length of the sub-calibre projectile.
 10. The ammunition according to claim 1, wherein the prolonged part of the sub-calibre projectile incorporates plane faces aligned on the longitudinal axis of the sub-calibre projectile onto which the blades are folded back in their folded position. 